There are, existing in the prior art, numerous actuating devices which function to convert linear motion to rotary motion or alternatively rotary to linear motion through utilization of ball screw actuating mechanisms. Such prior art devices are exemplified by those illustrated in U.S. Pat. Nos. 2,197,155, 2,705,939, 2,804,054, 3,062,070, 3,162,098, 3,192,783, 4,134,329, 4,199,999, 4,290,344, 4,325,535, British Patent No. 890,440 Feb. 28, 1962, and in Soviet Union Patent Nos. 397,688 Jan. 24, 1974 and 784,429 May 17, 1980.
The devices illustrated in the prior art function to provide the desired linear to rotary or rotary to linear motion conversion quite adequately. However, the devices illustrated are, where high power output is required, quite bulky and heavy. If a device of the prior art type is light in weight or is relatively small, then the power output is quite small.
The present invention is particularly adapted for utilization in aerospace vehicles to position a flight control surface. More particularly the device is intended to be used in such a manner that the axis of the actuator's rotary output is coincident with the hinge line axis of rotation of the flight control surface. Therefore, the rotary actuator envelope restrictions are such that the actuator must fit within the basic aerodynamic mold lines of the airfoil of which the control surface is a part. At the same time, the actuator has a relatively high power output to position the control surface, particularly when the aerospace vehicle is traveling at high speeds.
None of the prior art devices exemplified by those illustrated in the above-referred-to patents are capable of meeting the required low profile high power to weight and high power to volume required for a hinge line actuator for an aerospace vehicle control surface.